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Cassini Spacecraft Images Seas on Saturn's Moon Titan

03.13.07

Instruments on NASA's Cassini spacecraft have found evidence for seas,
likely filled with liquid methane or ethane, in the high northern latitudes
of Saturn's moon Titan. One such feature is larger than any of the Great
Lakes of North America and is about the same size as several seas on Earth.

Cassini's radar instrument imaged several very dark features near Titan's north
pole. Much larger than similar features seen before on Titan, the largest dark
feature measures at least 100,000 square kilometers (39,000 square miles). Since
the radar has caught only a portion of each of these features, only their minimum
size is known. Titan is the second largest moon in the solar system and is about
50 percent larger than Earth's moon.

"We've long hypothesized about oceans on Titan and now with multiple instruments
we have a first indication of seas that dwarf the lakes seen previously," said Dr.
Jonathan Lunine, Cassini interdisciplinary scientist at the University of
Arizona, Tucson.

While there is no definitive proof yet that these seas contain liquid, their shape,
their dark appearance in radar that indicates smoothness, and their other properties
point to the presence of liquids. The liquids are probably a combination of methane
and ethane, given the conditions on Titan and the abundance of methane and ethane
gases and clouds in Titan's atmosphere.

Cassini's visual and infrared mapping spectrometer also captured a view of the region,
and the team is working to determine the composition of the material contained within
these features to test the hypothesis that they are liquid-filled.

The imaging cameras, which provide a global view of Titan, have imaged a much larger,
irregular dark feature. The northern end of their image corresponds to one of the radar-imaged
seas. The dark area stretches for more than 1,000 kilometers (620 miles) in the image,
down to 55 degrees north latitude. If the entire dark area is liquid-filled, it would
be only slightly smaller than Earth's Caspian Sea. The radar data show details at the
northern end of the dark feature similar to those seen in earlier radar observations of
much smaller, liquid-filled lakes. However, to determine if the entire dark feature is a
liquid-filled basin will require investigation through additional radar flyovers later
in the mission.

Image left: This image is a portion of a larger view of Titan that features some of the largest bodies of liquid ever seen. The lake on the far right is larger than any lake on Earth and could be legitimately called a sea. Image credit: NASA/JPL+ Full image and caption

The presence of these seas reinforces current thinking that Titan's surface must be
re-supplying methane to its atmosphere, the original motivation almost a quarter century
ago for the theoretical speculation of a global ocean on Titan.

Cassini's instruments are peeling back the haze that shrouds Titan, showing high northern
latitudes dotted with seas hundreds of miles across, and hundreds of smaller lakes that
vary from several to tens of miles.

Due to the new discoveries, team members are re-pointing Cassini's radar instrument during
a May flyby so it can pass directly over the dark areas imaged by the cameras.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and
the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena,
manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington.
The Cassini orbiter was designed, developed and assembled at JPL.